The present invention relates to non-edible collagen casings for food products which do not have to be soaked in water or brine just before stuffing (ready-to-stuff casings), and the method for preparing them. More specifically, the invention refers to a preparation of a stabilized longlife non-edible collagen casing ready-to-stuff comprising a moisture amount between 27% and 50% by weight based on total casing weight and a salt amount between 2,5% and 30% by weight based on dry casing weight, wherein the salt comprises a salt from an organic acid and wherein the casing is packed.